Bending machine

ABSTRACT

The bend-straightening machine (100) for workpieces (20) that are more long than wide, such as camshafts, pinion shafts, and similar items, includes one or more straightening dies (14) that bring about on the workpiece (20), between straightening bases that are placed on the machine table (10), a change in the shape of a bend. The straightening die (14) is mounted on a swiveling mechanism (30), which includes a two-armed lever (36) that can swivel around an axle (32&#39;) and that protrudes from the axle (32&#39;) on both sides. The straightening die (14) is joined with the one arm (36&#39;), while a drive (31) that causes the swiveling of the two-armed lever (36) acts upon the free end (36&#34;) of the other arm. (FIG. 1)

The invention pertains to a bend-straightening machine of the type forwork pieces that are longer than they.

BACKGROUND

With the bend-straightening machine, the straightening is carried out inaccordance with DE 34 45 544 A1, in which the workpiece, a pinion shaftor a camshaft for example, is deflected between two bases by astraightening die at the point at which an impact is present until apermanent change in shape occurs that is opposed to the impact andneutralizes it. The location of the impact is determined by rotating theworkpiece through appropriate measuring devices in the longitudinal andcircumferential directions. Either an individual straightening die isdisplaced in an appropriate fashion along the fixed workpiece in thelongitudinal direction, or the workpiece is displaced in thelongitudinal direction past a fixed straightening die, or there areseveral straightening dies present which are distributed over the lengthof the workpiece and which can be actuated as needed.

Usually, the workpiece is supported in a rotating fashion between centerpoints that act as the workpiece seat. The straightening bases on whichthe workpiece is lying absorb the forces of the straightening die. Inthe case of a specific workpiece, a series of which are to bestraightened, they remain at fixed locations when viewed in thelongitudinal direction of the workpiece.

In general, the straightening die, which is attached to an upper part ofthe machine, is driven vertically by means of a hydraulicpiston/cylinder unit. In the cases mentioned, the upper part of themachine is configured either as an upper crosspiece of a double-columnpress, or as an upper crosspiece of an open-front press with oneC-shaped stanchion. In both cases, with the known bend-straighteningmachines of this type, it is necessary for a solid upper machine part toextend out over the workpiece to support the operating mechanism, ormore specifically, the drive for the straightening die. For its part,this drive has a certain size, since the piston/cylinder unit has tohave a specific cross-section because of the forces that arise, andtherefore has to have a specific length because of the necessary lengthof the piston travel. In the case of U.S. Pat. No. 2,276,941, above theC-shaped stanchion a two-armed lever is supported, one arm of which actsupon a vertical spindle that carries the straightening die, and on theother arm of which a drive cylinder located behind the C-shapedstanchion acts.

In a different version, as is known from DE 26 06 061 A1 for example,the entire bend-straightening machine is rotated by 90°, so that thestraightening force is exerted horizontally and the straightening basesand the straightening die are moved into a horizontal plane transverselyto the longitudinal direction of the workpiece. With this type ofbend-straightening machines as well, which usually exhibit a similarmachine stanchion in the shape of a "C", the force that is acting uponthe straightening die or dies is generated by means of one or morehydraulic piston/cylinder units at a part of the machine that is locatedto the side, and ahead of the workpiece, and that corresponds to theupper part of the machine in the upright version that was mentionedearlier.

The document SU-A1-1404 141 contains a hydraulic swiveling two-armedlever in which the straightening die is fastened to the free end of oneof the arms and moves in the arc of a circle during straightening.

All known bend-straightening machines exhibit a considerable size as aresult of the upper part of the machine or, ill the case of thehorizontal of the horizontal version, the side part that corresponds tothe upper part of the machine. The construction effort that is neededfor the frame and the stand is increased even further as a result of thepiston/cylinder units that form the single, straight-line hydraulicdrive for the straightening die.

SUMMARY OF THE INVENTION

The invention performs the task of designing a bend-straighteningmachine, in such a way that size, structural expenditures, and powerconsumption during operation are all reduced.

In accordance with that, the straightening die or dies are actuated bymeans of a swiveling mechanism. Thus, the propulsion of thestraightening die is no longer carried out by means of a linear drivethat acts from outside directly against the workpiece and that requiresa corresponding amount of space, but is instead carried out by means ofa swiveling arrangement that permits a displacement of the drivemechanism from a position that is radial to the workpiece, and so allowsa much more compact style of construction. By the swiveling drive, whatis meant is the drive during the-straightening stroke, that is, duringthe exertion of force, and not the displacements of the straighteningdies that might have to be responded to in the form of a swivelingmovement in order to bring them into the straightening position, nor thepossible corresponding workpiece displacements workpiece before thestraightening procedure takes place. The structural expenditure for theprotruding machine or side parts and for the carriage on which thestraightening dies are mounted and guided, and which, as a result offorces that often occur off-center, has to be made especially secureagainst tilting and therefore correspondingly large, is significantlylarger than the structural expenditure for the swivel drive of thestraightening die.

Even the first straightening machines that were structurally executed inaccordance with the invention have demonstrated that the design volumecan be reduced by as much as 40 percent by means of the invention, withthe same performance.

The swiveling mechanism is arranged in such a way that the straighteningdies exert a force at the location of the workpiece that is, as before,essentially perpendicular to the workpiece and opposite to thestraightening bases. What is particularly advantageous about thebend-straightening machine in accordance with the present invention isthe fact that the swiveling drive can be implemented underneath the dragbearing of the two-armed lever, or more specifically, under the machinetable below the height of the working procedure. As a result of this,the design heights above the workpiece can be kept small andaccessibility for the automatic feed devices can be improved, and theswiveling drive remains within the contours of the straighteningmachine, that is, the drive does not protrude from the top and/or backas is the case with the state of the art.

The straightening dies move in the arc of a circle during the swiveling.The error in the directing of the straightening force that is linkedwith that is, however, unimportant, since with the workpieces that areto be processed, a straightening stroke of a maximum of 20 mm issufficient, and the swivel arrangement can be laid out and dimensionedin such a way that the straightening die in the region of thestraightening stroke is displaced only slightly to the side relative tothe center of the workpiece. This excursion amounts to less than 5°/ooof the straightening stroke, and thus has no effect on the straighteningstroke.

Sometimes, such as when straightening bends in workpieces that have alarge cross-section and strong deflection, for example, in the case ofrolled steel sections for girders and rails, a massive machine upperpart with a hydraulic piston/cylinder unit as drive mechanism cannot beavoided. In many cases, however, smaller workpieces that are lessresistant to bending are involved, such as pinion shafts, camshafts ordriveshafts, for example, which are common in large numbers in theautomobile industry, or profile sections of small cross-sections,particularly those made of aluminum, with which there are no largecross-sections and long straightening die strokes are not necessary. Itis for goods needing straightening such as these that the invention isprimarily intended.

In addition, in a preferred embodiment the swiveling axis of the dragbearing for the two-armed lever is placed parallel to the longitudinalaxis of the workpiece, even though forms of implementation that arecross-wise to the longitudinal axis of the workpiece are not excluded inprinciple.

The implementation permits a manner of construction in which only thestraightening die and its carrier arrangement are located above theworkpiece.

Other developments of the two-armed lever, in which the forces of thedrive mechanism act, include acting cross-wise to the direction of onearm, in one instance and in the same direction as the arm in anotherinstance.

The swiveling constructional unit can act upon one individualstraightening die, which is joined with it. Usually, however, there areseveral straightening dies distributed or placed movably along theworkpiece, so that the arrangement of the straightening dies exhibits acertain extension along the workpiece.

For that purpose, each straightening die is no longer assigned its ownswiveling mechanism.

The arrangement of the straightening dies is also a feature of theinvention.

The drive is implemented, in one possible form of implementation, as alinear drive.

In another embodiment, the drive can act immediately upon the other,free end of the two-armed lever, and a transmission with varyingvelocity ratio can also be placed in between.

Embodiment of the drive mechanism includes a rotating cam plate, whichoffers the advantage that the progression of the drive, and thus theprogression of the stroke as well, can be freely selected.

In conjunction with this, it is beneficial if the axis of the cam plateis placed vertically underneath the free end of the other, essentiallyhorizontal, arm of the two-armed lever.

In this way, the drive can be displaced into the lower region of themachine pedestal, and the space near the workpiece remains free of driveparts.

The attaining of sufficient clearance between the two-armed lever andthe cam plate also serves for the provision of a force transfer link.

The invention can also be put into practice in any desired combinationsof the features contained in the claims, while making use of featuresmentioned in the description as well.

Implementation examples of the invention are represented in thedrawings, which illustrate various embodiments that the invention maytake in physical form and in certain parts and arrangement of partswherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a representation of the essential parts of a first form ofimplementation of the bend-straightening machine;

FIG. 2 shows a side view of the complete bend-straightening machine ofthis form of implementation;

FIG. 3 shows a side view in accordance with FIG. 2, in partialcross-section without the conveyor apparatus for the workpieces;

FIG. 4 shows a view, corresponding with that of FIG. 1, of the essentialparts of a second form of implementation of the bend-straighteningmachine;

FIG. 5 shows a corresponding view of a third form of implementation.

PREFERRED EMBODIMENTS

In FIG. 1, the workpiece 20 is shown schematically as a cylindrical bodythat is more long than wide, the axis of which runs perpendicular to theplane of the drawing. In practice, the contours of the workpiece 20 cancertainly be irregular as well. For example, camshafts, driveshafts forvehicles, pinion shafts, or similar items can be involved.

The workpiece 20 lies upon straightening bases, which are not shown inFIG. 1, which exhibit a distance from each other in the direction of theaxis, and which are placed on the fixed machine table 10. Between thesestraightening bases, the straightening die 14 acts, by means of aswiveling apparatus that is designated in its entirety as 30, upon theworkpiece 20 from above, and deflects it to a desired extent downward,opposite an impact that is present and that, by means of turning theworkpiece 20, is displaced upward, in order to bring about on theworkpiece 20 a permanent, straightening change in shape that neutralizesthis impact.

The straightening die 14 is attached to a straightening hammer 18, whichis only shown schematically in FIG. 1 by means of a dashed line, andwhich is in turn fastened, by means of a dovetail, to the underside of aswiveling head 37 that protrudes approximately horizontally over theworkpiece 20 from the side. The swiveling head 37 is seated on acoupling link 33, which extends parallel to the workpiece 20 and isconfigured as a tube, and which is attached at one of its ends to thefree end of an arm portion 36' of a lever 36. Arm portion 36' is uprightwhen in the straightening position. Lever 36 has two arm portions, theaforementioned portion 36' and the lower portion 36". Lever 36 issupported in the center in a swiveling manner by a drag bearing 32, theswiveling axis 32' of which extends parallel to the workpiece axis.

The lever 36, rotates about the drag bearing 32. The other arm portion36" bends slightly away from the workpiece 20 by a slight angle 19, 18°in the implementation example, relative to the arm 36'. This is done sothat it is possible to place the drive spindle 35, which is a part ofthe swiveling drive 31 of the lever 36, as centrally as possible underthe workpiece 20. The drive spindle 35 protrudes from the lever 36 andcross-wise to it, towards the same side as the swiveling head 37 underthe machine table 10, and is driven by an electric motor 34 that isshown in FIG. 2, which is indicated by the arrow 45 in FIG. 1.

On the spindle 35 there is placed, in accordance with FIG. 3, a spindlenut 46, which has side bearing journals 47 that are supported in thebearings in the eyes of the fork cheeks 48 that are placed on both sidesof the spindle nut 46. The fork cheeks 48 are attached to the lower endof the other arm 36" of the two-armed lever 36.

When the drive spindle 35 turns in the direction of the arrow 45, thespindle nut 46 is displaced in the direction of the arrow 39, andswivels the lever 36, as a result of which the fork cheeks 48 that arejoined with it turn around an axle 49 in FIG. 1, which runsperpendicular to the plane of the drawing, with respect to the spindlenut 46. At its right end as shown in FIG. 1, the spindle 35 is supportedfirmly at the machine in bearings 44, which are capable of dealing withthe slight swiveling of the spindle 35 that takes place during thedisplacement of the spindle nut 46 or the two-armed lever 36. Thebearings 44 are either configured as self-aligning bearings, or theyhave sufficient play around the transverse axis. The stroke that takesplace in practice is not particularly large. A limit position of thetwo-armed lever is shown in FIG. 1 in a dotted line position in whichthe straightening die 14 has been lifted from the workpiece 20, and theworkpiece can be changed. If the straightening die 14 were to be moveddownward and work its straightening stroke, the spindle nut 46 would bedisplaced to the left as a result of the corresponding turning of thespindle 35 in accordance with FIG. 1.

From FIG. 1 it can be seen that the drive 31 of the straightening diedoes not protrude from the workpiece 20 towards the outside and beyondthe ground plan of the machine, but rather, is to a certain extentplaced around the workpiece in a space-saving way.

In FIGS. 2 and 3, the bend-straightening machine 100, in which thearrangement in accordance with FIG. 1 is used, is represented in itsentirety. It includes a common machine stand 50, and placed on it is themachine stand 10, on which the workpiece seats 12 are built. In theimplementation example, the workpiece seats 12 have the shape of centersleeves with center points 13, which engage with correspondingcounter-sunk areas in the ends of the rod-like workpiece 20. Severalstraightening bases 16, which support the workpiece 20 against the forceof the straightening die 14 that moves against it from above, aremounted on a positioning rail, and can be displaced, by means of onedrive mechanism 22 each (FIG. 2), transversely to the axis of theworkpiece 20 as well as in the workpieces longitudinal direction. Thestraightening dies 14 can likewise be displaced along a positioningrail, by means of drive mechanisms 23, transversely to the workpiece 20as well as in the workpiece's longitudinal direction. The mountingassembly of the straightening die 14 at the swivelling head 37 forms theso-called straightening hammer 18, to which the straightening die 14 isattached by means of a dovetail guide. In the implementation example(FIG. 3), there are three straightening dies provided, but other numberscan also come into consideration. The radial run-out of the workpiece20, that is, the "impact", is measured with calipers 17, four of whichare present in the implementation example.

During the straightening procedure, the swiveling head 37 with thestraightening die 14 is pressed downward against the workpiece 20 by thelever 36. In the implementation example, there are two swiveling heads37 present (FIG. 3), which exhibit distance between them in thelongitudinal direction of the workpiece 20, and which jut outessentially horizontally. They are attached to a connecting link 33,which is configured as a solid tube and which extends along theworkpiece 20, and which is joined at one end with the upper end of theone upright arm portion 36' lever 36, and at the other end with theupper end of a lever 56, which matches the arm 36' in size andorientation, and which is supported in a swiveling fashion at theopposite end, in the longitudinal direction of the workpiece 20, of themachine table 10 in a bearing 52 that corresponds to the bearing 32 ofthe two-armed lever 36.

In this implementation example, the lever 36' is thus provided only onone side, and the one-armed lever 56, which is joined by means of theconnecting link 33 and the arm portion 36' to a torsion-resistantconstructional unit 30, is simply moved along with it.

It will be appreciated that a second two-armed lever 36 with its owndrive mechanism carried out by means of a synchronized rotating spindle35 could also be provided at the other end. In the same way, in place ofthe fork cheeks 48, an additional tubular connecting link could beprovided, and could engage with a single linear drive at the drive'scenter.

In the implementation example in the drawing, the drag bearings 32, 52are mounted with their self-aligning axles exactly at the height of theaxis of the workpiece 20 that is to have its bend straightened.

Since, when the straightening die has gone down and is just about to actupon the workpiece 20, the arms 36', 56 are directed approximatelyvertically upward from the drag bearings 32, 52., and the swiveling head37 is jutting out approximately horizontally, this results in a geometryin which the effective direction of the straightening die 14 over thecourse of the straightening stroke under consideration acts nearlyexactly vertically downward against the workpiece 20 and thestraightening bases 16 that are supporting it. The angular deviation isso slight that it is insignificant in practice.

The Workpieces 20 are conveyed forward and backward by means of awalking beam conveyor 40, which can be seen only in FIG. 2. The walkingbeams 42, 44 extend through the machine cross-wise to the workpieces 20,and convey the workpieces in increments until they are suspended betweenthe center points 13, and then to the workpiece discharge 43 after thestraightening of the bend has taken place. The actuation of the walkingbeams 42, 44 is carried out by means of stroke mechanisms 41.

In an additional implementation example, which is designated in itsentirety by 200 in FIG. 4, the swiveling constructional unit 230 isdriven by a linear drive 231, which, as in FIG. 1, includes a rotatingspindle 35 that is supported at the right end in a bearing 44 in fixedfashion at the machine. Two connecting links 238, 239, which are ofapproximately the same length in the implementation example, carry forkcheeks 248, 250 on the ends that face each other, overlap the opposingsides of a hinge block 235 that forms the spindle nut, and are supportedon bearing journals 240 that protrude from the hinge block 235 in such away that they can swivel around a common axle 249.

The spindle 35 engages with a spindle screw thread in the hinge block235, so that the hinge block 235 is, for example and in accordance withFIG. 4, displaced to the right during corresponding rotation of thespindle 35. In conjunction with that, the connecting links 238, 239swivel around the axle 249.

The lower end of the lower connecting link 238 is supported in a bearing241 that is fixed to the machine, the upper end of the upper link 239 ina bearing 234 at the free end of the lower, essentially horizontal armportion 236" of the lever 236. The one arm portion 236' of the lever 236runs approximately vertically in an upward direction, and carries theswiveling head 237, which, just like in FIG. 1, juts out approximatelyhorizontally over the workpiece 20, and is attached to the tubularconnecting link 233.

The lever 236 is supported at its apex in a bearing 232 on the upperside of the machine table 10, and can swivel around its axle 232'.

In the position shown, which roughly corresponds to the beginning of thestraightening stroke, the two connecting links 238, 239 form a smallangle 219 of approximately 30°with each other, the bisecting line ofwhich is given by the axis of the spindle 35. The connecting links 238,239 thus form a toggle mechanism that presses the arm 236", which isessentially horizontal and which projects downward from the workpiece20, upward during a displacement of the hinge block 235 to the right,and thus swivels the lever 236 in the direction of the straighteningstroke. The smaller that the angle 219 is, the stronger is thetransmission of the force from the spindle 235 that is carried out bymeans of the toggle mechanism 238, 239. The arrangement is made in sucha way that in the shown position of the toggle mechanism 237, 238 andthe lever 236, which corresponds to the start of the straighteningstroke, there is a smaller angle 219, and when the swivel head is liftedinto the position indicated with dotted lines, a displacement of thetoggle mechanism 238, 239 into the region of the larger angle 219 takesplace, so that a sudden rapid movement takes place and an optimallytransferred action by the force is carried out in the actual work area.

In FIG. 5, a third form of implementation 300 of the straighteningmachine is shown, in which there is placed at the machine pedestal 50and under the machine table 10 a drive motor 34 that acts upon astep-down gear system 315, at which a cam plate 320 can rotate on ashaft 318 around an axle 319 that is perpendicular to the plane of thedrawing. At a point 325 that is located vertically above the axle 319, arotating roller 312 at the lower end of a vertical force transfer link323 rolls on the cam plate 320. At its upper end, the force transferlink 323 is placed at the right end of the essentially horizontal armportion 336" of a lever 236 having two arm portions. The lever 336 canswivel on a bearing 332 that is fixed to the machine around an axle 332'that is parallel to the workpiece 20. From the bearing 332, the arm 336'extends in an upward direction and juts out over the workpiece 20 to theleft in accordance with FIG. 5, so that to a certain extent, whencompared to FIG. 1 the arm 36' there and the swiveling head 37 areformed from one part. The lever 336 is formed by means of a plate, butcarries out the function of the previously described lever embodimentsas a result of the arrangement of the points of application of force.

The force transfer link 323 and the lever 336 together form theswiveling mechanism 330. The force transfer link 323 is guided in anessentially vertical direction by means of a connecting link 324 that ishinged at the side at its lower end that extends essentiallyhorizontally to a fixing point on the machine pedestal 50, so that thepoint of contact 325 always remains essentially vertical above the axisof rotation 319 of the cam plate 320.

During rotation by the cam plate 320, the force transfer link 323 iseither lifted up or drops down. The shape of the curve of the cam plate320 can be chosen in such a way that an important multiplication offorce is provided within the range of the straightening stroke, and whenthe straightening die 14 is lifted from the workpiece 20, particularlyduring the final phase, so that a quick stroke takes place with rapidmovement.

As is the case with the form or implementation in accordance with FIG.2, the workpieces 20 are transported through the straightening machine300 by means of a walking beam mechanism 40.

The arrangement shown, with cam plate 320, force transfer link 323, andtwo-armed lever 336, is present at both of the opposite ends, in thelongitudinal direction of the workpiece 20, of the machine table 10. Thecam plates 320 placed there are linked by the shaft 318. The two levers336 form a unified, torsion-resistant structural unit 330 by means ofthe connecting link 333, which likewise extends in the longitudinaldirection of the workpiece 20 and which is formed by a box girder.

The straightening machine 300 of FIG. 5 is especially preferable, notonly because it reduces the structural expenditure when compared withthe usual straightening machines, but also because the energyconsumption can be lowered to almost one third as a result of themechanical actuation by means of the cam plate 320 and the electricmotor 334.

Having thus described the invention, it is claimed: 1.Bend-straightening machine for workpieces having longitudinally oppositeends that are more long than wide, said machine includingworkpiece seatsand a machine table, said workpiece seats placed on and above saidmachine table to hold the ends of the workpiece so it can rotate, atleast two straightening bases that are at a distance from each otheralong the longitudinal direction of the workpiece, said twostraightening bases support the workpiece placed on the machine table,at least one straightening die that acts upon the workpiece between thestraightening bases, and a lever having two arm portions and a centerportion therebetween, said lever being supported in the center portionin a drag bearing that is fixed to the machine, each said arm portionhaving a free end, swivel drive means for actuating said lever, saidstraightening die being fastened at the free end of one said arm portionto move in the arc of a circle during swiveling, said swivel drive meansacting upon the free end of the other said arm portion in a directiontransverse to said longitudinal direction, said bend-straighteningmachine comprising said swivel drive means being an electric motor fordriving a drive spindle that is placed under said machine table.
 2. Thebend-straightening machine of claim 1, wherein said drag bearingincludes an axis of rotation that is placed parallel to the longitudinalaxis of said workpiece.
 3. The bend-straightening machine of claim 1,wherein said drag beating is placed approximately at the height of saidworkpiece and one of said arm portions extends upwardly therefrom andessentially upright.
 4. The bend-straightening machine of claim 3,wherein one said arm portion of said lever is bent from said workpieceand away from said other arm portion at an angle of from 10° to 40°. 5.The bend-straightening machine of claim 3, wherein one said arm portionof said lever is bent from said workpiece and away from said other armportion at generally a right angle.
 6. The bend-straightening machine ofclaim 1, wherein said machine table has ends that are opposite eachother in the longitudinal direction of the workpiece, said lever at oneend of said table, and a second lever at said opposite end of said tableincluding second swivel drive means for actuating said second lever eachof said drive means being synchronized and are linked with each other bymeans of a connecting link that extends parallel to the longitudinaldirection of said workpiece, to form a constructional unit that canswivel.
 7. The bend-straightening machine of claim 1, wherein said tableincludes two longitudinally opposite ends, said lever being placed atone end of said machine table, that at the opposite end of the table asecond lever having only one arm portion is supported in an additionaldrag bearing that is aligned with the drag bearing of said lever, a onearmed lever that extends parallel to one said arm portion of said leverand is of a generally equal length, and that said second lever and saidone said arm portion are joined with each other by means of a connectinglink that extends parallel to the longitudinal direction of saidworkpiece.
 8. The bend-straightening machine of claim 6, wherein saidstraightening die is placed at said connecting link.
 9. Thebend-straightening machine of claim 8, wherein said straightening die isplaced at said connecting link by means of a swiveling head thatprotrudes from said connecting link essentially horizontally above saidworkpiece.
 10. The bend-straightening machine of claim 1, wherein saidswivel drive means is a linear drive.
 11. The bend-straightening machineof claim 10, wherein said straightening die is attached to a swivelinghead, said swiveling head and said linear drive extend in the samedirection.
 12. The bend-straightening machine of claim 5, wherein saidswivel drive means acts upon said lever by means of a transmission withvarying velocity ratio.
 13. The bend-straightening machine of claim 12,wherein said transmission with varying velocity ratio includes twoconnecting links that are supported in a rotating manner on a hingeblock, said connecting links forming a small angle with each other, eachsaid connecting link having ends opposite said hinge block, one saidconnecting link being connected with the free end of one said armportion at a bearing, and said swivel drive means acting upon the hingeblock to bring about a toggle effect.
 14. The bend-straightening machineof claim 13, wherein said connecting links are supported at said hingeblock by fork cheeks that overlap said hinge block.
 15. Thebend-straightening machine of claim 14, wherein said fork cheeks aresupported at said hinge block on a common axle.
 16. Bend-straighteningmachine for workpieces having longitudinally opposite ends that are morelong than wide, said machine includingworkpiece seats and a machinetable, said workpiece seats placed on and above said machine table tohold the ends of the workpiece so it can rotate, at least twostraightening bases that are at a distance from each other along thelongitudinal direction of the workpiece, said two straightening basessupport the workpiece placed on the machine table, at least onestraightening die that acts upon the workpiece between the straighteningbases, and a lever having two arm portions and a center portiontherebetween, said lever being supported in the center portion in a dragbearing that is fixed to the machine, each said arm portion having afree end, swivel drive means for actuating said lever, saidstraightening die being fastened at the free end of one said arm portionto move in the arc of a circle during swiveling, said swivel drive meansacting upon the free end of the other said arm portion in a directiontransverse to said longitudinal direction, said bend-straighteningmachine comprising said swivel drive means being an electric motor fordriving a cam plate that is placed under said machine table.
 17. Thebend-straightening machine of claim 16, wherein said electric motordrives said cam plate in a rotating fashion around an axle that is fixedto said machine.
 18. The bend-straightening machine of claim 17, whereinsaid axle of said cam plate is placed vertically underneath the free endof one of said arm portions of said lever.
 19. The bend-straighteningmachine of claim 18, including a force transfer link having an upper andlower end, said upper end linked to said lever, said cam plate actingupon said lower end to provide vertical actuation of said transfer link.20. The bend-straightening machine of claim 19, wherein said forcetransfer link is guided by a transverse link that is pivotably fixed tosaid force transfer link adjacent said lower end.